L&L Express stuttering

I'm trying out Lock and Load Express with Final Cut Express, and am having trouble getting it to look right. The results are very, very choppy -- the clips with L&LE applied play with pronounced stuttering, that is, the scene jerks around a lot so much that the scene is unusable. What would cause this? Thanks.

I wish it were that easy. Yes, I've rendered the clip, and I'm not using Unlimited RT. I even exported it the clip as a Qucktime movie, to see if it was just a problem with playback within FCE, but alas, the quicktime movie had the same problem. I must be doing something wrong -- I have heard very good things about L&L and I know my results must not be normal. Thanks for any help you can provide.

Your comment made me go and look at the sequence settings and I had indeed set them for 720 when the source clip was 1080. I had thought that FCE adjusts the sequence to the clip -- a dialog box pops up when I put in a conflicting clip, saying it would automatically adjust fce sequence settings -- but I guess not. Setting it to 1080 when I created the project fixed it -- L&L Express worked great. Is this what you were referring to by field order? Or is there a different setting I ought to look at to get even better results? Thank you for your help.

I think FCE should setup the sequence with correct width, height, and pixel aspect ratio.
If they're not correct, this might cause such problems as well.
I was considering that the field order was not correct.
Is it 1080 interlaced or progressive? I know that FCP/E does not always detect this correctly.
If it looks good on an interlace capable screen, it should be ok.